I have to find the potential energy and the kinetic energy and its total of an object of mass 20 kg falls freely from 4m high from the ground level and the gravity due to earth is being taken as 10 m/s.

height Potential Energy Kinetic Energy Total
(1) (2) (3) (4)

4m

3m

2m

1m

just above the ground.

Here to calculate the Kinetic Energy at 3m,
I took s = distance = 1m;
u = initial velocity = 0;
and used the formula s = ut + 1/2 at^2
and found the time t;